ISSUE 2   May 11, 2000

WHIP WEEDS AT THEIR WEAKNESS

    In the recent corn survey for the 1999 season, respondents named several weeds as problems in corn. The most commonly cited weed woes included: foxtail, Canada thistle, wild proso millet, black nightshade, kochia, common cocklebur and quackgrass. These scary seven specters in the corn field are troublesome due to their appearance and disappearance in fields despite concerted efforts at elimination. The biology of the corn culprits may be a clue to the reason these weeds are so difficult to whip in corn. The foxtail, or pigeongrass, complex has several family members but the most common relatives are the giant, green and yellow foxtails. Giant foxtail is an imposing foe which can germinate with or without light at 59-86F. It can even emerge from almost 5 inches in the ground! Green foxtail can germinate in soil from 50-95F, but prefers temperatures below 86F and depths of 3 inches or less. Germination is best at 1.5 inches into the ground. Yellow foxtail likes to germinate at 68-77F in either light or darkness from 1.5 inches in the soil. Canada thistle germinates best in bright daylight with an
8-16 hour photoperiod within the upper inch of soil with 50-104F but prefers 86F. Wild proso millet has no light response and can germinate from 50-104F but operates best in 86F. Black nightshade has little dormancy in the seed once separated from the berry but light can enhance the germination process especially at 68-113F, with best responses at 86F. Kochia can more easily germinate within a light requirement but it doesn’t need this factor. Kochia prefers temperatures of 59-86F but can run the gambit on the pH scale, germinating in soils from pH 3 to 11! Common cocklebur doesn’t require light to germinate
but has differences in temperature response depending on seed location in the bur. Those seed at the base of the bur germinate without light at 72-122F while those at the distal end of the bur require red light and temperatures of 77-106F. Quackgrass regrows by either rhizomes or seed. Rhizome growth progresses well at 59-68F while the seed can germinate with or without light at 59-77F and it lacks any innate dormancy. Not surprisingly, many of the weeds germinate around 86F, a warmer temperature than when corn is first planted thus by-passing early burndowns or cultivations. Use your knowledge of each field’s weed seed bank to cut down on these corn culprits.

Denise A. McWilliams
Extension Crop Production Specialist
dmcwilli@ndsuext.nodak.edu

    The North Dakota Weed Control Association has scheduled training sessions for non-cropland weed control personnel at two locations this year. Topics to be covered include noxious and invasive weed identification, herbicide drift avoidance, equipment calibration, and safe use of pesticides. The Williams County Weed Board will host the first session in Williston, ND, on Monday May 22, 2000. The second session will by hosted by the Cass County Weed Board and the NDSU Plant Sciences Dept., on Thursday, May 25, 2000 in Loftsgard Hall on the campus of NDSU.

The complete agenda for both schools:

8:45am - Registration

9:00am - Right-of-Way Certification, Andrew Thostenson

9:30am - New Invasive and Nasty Weeds, Rod Lym

10:15am - Herbicide Drift Avoidance & Consequences, Vern Hoffman

10:45am - State, National, and Global Issues, Andrew Thostenson

11:45am - Lunch ($6)

1:00pm - Herbicide Update, Rod Lym

1:20pm - Equipment and Calibration, Vern Hoffman

2:30pm - Enhancing Safety by Reading Labels Properly, Andrew Thostenson

The spring sprayer schools serve as a brush-up course for new and returning weed control personnel. The course offers Pesticide Certification in the Right-of-Way category and is open to all those interested.

Rod Lym
Perennial/Noxious Weed Scientist
lym@plains.nodak.edu